JAYAPURA, Indonesia — Protesters killed four security officers after clashes broke out Thursday during a rally demanding the closure of a U.S.-owned gold mine in Papua. The officers were either hacked or burned to death, police and witnesses said. Dozens of people were also wounded in the day-long protests, some seriously.

It was the third day of violent protests against the mine run by Freeport-McMoRan Copper & Gold Inc. The killings are certain to sharply raise tensions in the region, which is also home to a separatist rebellion.

"The killers are no longer human beings," said police spokesman Col. Kertono Wangsadisastra. "They went wild."

Hundreds of protesters blockaded the road outside a university in the provincial capital Thursday demanding the government close the gold mine, said to be the world's largest. Riot police tried to break up the rally with tear gas and baton charges, but the rock-hurling students refused to move.

Several security officers shot at protesters, though police Lt. Col. Paulus Waterpauw claimed they were firing rubber bullets or blanks.

He said three policemen and one soldier were killed after they were run down by a frenzied mob, two bludgeoned with rocks and knives and the others set on fire.

Hospitals said at least 19 police and eight protesters were injured, many of them seriously.

Protests force temporary closureFreeport's mine is often held up by independence supporters as a symbol of the unfair division of resources between the capital and Papua, while its practice of paying soldiers to guard the facility is also deeply unpopular.

There have been several rallies against the gold mine in recent weeks, including one on the road leading to the mine that forced it to temporarily suspend operations, costing the New Orleans-based company millions of dollars.

"We want Freeport to close because it has not given any benefits to the people of Papua, in fact it's made them suffer," said protester Kosmos Yual.

Sporadic clashes continued throughout the afternoon, with gun shots repeatedly heard across the city, though it was not clear who was firing. Journalists were ordered away from the scene.

Wangsadisastra said at least 10 people were arrested but that members of the mob who killed the officers had fled into a nearby jungle.

Freeport defends its operations in the highlands of Papua, saying it pays millions of dollars in taxes each year and funds scores of community projects close to the mine.